Hearing aid compatibility (HAC) is generally directed to making devices such as telephones, which supply a conventional acoustic signal, compatible for use with devices that assist hearing, such as hearing aids. HAC involves generating a magnetic audio signal (which is inaudible) from or near the earpiece area of a mobile telephone. The magnetic audio signal is provided by a changing magnetic field which is encoded with audio information. The magnetic audio signal may be generated in addition to or instead of a conventional acoustic audio signal (which is audible). The magnetic audio signal is received by a receiving coil within the hearing aid. The receiving coil may be a telecoil (or T-coil). The hearing aid converts the magnetic audio signal received by the receiving coil into an acoustic signal. This acoustic signal, when emitted in the ear channel of a user, allows a hearing aid wearer to hear audio output from the telephone.